1. Technical Field
The present invention relates to information processing apparatuses, and more particularly to an information processing apparatus that can display a group of extracted images in the case of video printing.
2. Related Art
An increasing number of users enjoy playing back video streams using information processing apparatuses, such as photo viewers, personal computers, or the like. To play back a video stream using such an information processing apparatus, when a scene of the video stream can be printed as a group of image frames, this further enhances the user-friendliness of the information processing apparatus. For example, JP-A-2005-88533 discloses a technique for appropriately extracting, from a plurality of video frames constituting a video stream, images to print and printing the extracted images.
If such video printing is implemented, for example, a user who plays golf and wants to check his/her swing by capturing a video image of the golf swing and playing it back as a video stream feels it convenient to print a group of images extracted from the video stream at predetermined time intervals. Another user who plays baseball and wants to check his/her pitching form by capturing a video image of the pitching form and playing it back as a video stream feels it convenient to print a group of images extracted from the video stream at predetermined time intervals.
Video files containing image data necessary for generating video frames may be compressed using various data compression techniques to reduce the data amount. Therefore, a complicated decoding algorithm may be necessary to extract images to print from such a video file.
FIG. 1 describes the data format of Moving Picture Experts Group (MPEG)-1, which is a typical compression technique for video data. As shown in FIG. 1, MPEG-1 employs a group of picture (GOP) structure. Image data for generating video frames is classified into three types of pictures, namely, intra-coded (I) pictures, predictive-coded (P) pictures, and bidirectionally predictive-coded (B) pictures. I pictures are image data generated by encoding an input signal, without performing prediction. Since a video frame can be generated from an I picture, I pictures can be used as entry points, such as playback start points. P pictures are image data using single-directional motion compensation prediction. B pictures are image data using bidirectional motion compensation prediction. To generate a video frame from a P or B picture, a video frame(s) that precedes and/or follows the P or B picture must be played back, and then necessary motion compensation must be performed.
In the case that a plurality of extracted images that the user wants to print are composed of P pictures and B pictures, and that the extracted images are to be displayed as a group on a screen such that the user can check the images before printing, it takes a great amount of time to display the group of the extracted images, making the user's waiting time long. It thus takes a long period of time before the images are actually printed.